How or why do firearms advocates feel that everyone should have access to semi-automatic weapons and why would a "regular" person need semi-automatic weapons?

After last week’s massacre in the Newtown Elementary School, where this nut went in and shot the entire kindergarten class plus a bunch of other people, it came to light that the killer’s 52 year old mother owned the semi-automatic weapons that he used to do his killing. She was a seemingly ordinary middle aged, middle class woman. Why a woman like that would need semi-automatic weapons is beyond me. Now there is renewed attention on the issue of gun control. Firearms advocates are adamant about citizens’ rights to bear arms, including semi-automatic weapons.

Do you feel that everyone should have access to semi-automatic weapons? Why would a “regular” person (in other words, not a law enforcement officer or military personnel) need semi-automatic weapons? Do you think that the powerful gun lobby with their money thrown at politicians’ campaigns will ever be defeated?